Method of operating electric furnaces.



P. L. T. HEROULT. METHOD OF OPERATING ELEGTRIG FURNAGES APPLICATION FILED NOV. 13

Patented Mar. 2, 1909.

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FIG.

I/IIIl/I Ill IIHHH I I I I I I INVENTOR WITNESSES:

10 FURNACES. 13, 19,06.

EROUL G ELEGTR LED HOV.

P. L. T. H

METHOD OF OPERATIN APPLICATION I'I Patented Mar. 2, 1909.

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UNITED sTATEs PATENT OFFICE.

FAUli LQUIS TOUSSAINT HEROULT, OF LA PRAZ, FRANCE, ASSIGN OR TO SOOIETE ELECTRO- METALLURGIQUE FRANCAISE, OF FROGES ISERE, FRANCE.

METHOD OI OPERATING ELECTRIC FURNACES.

Specification of Letters Patent.

Patented 2, 1909.

Original application med lay 8, 1907, Serial No. 871,691. Divided and thin application filed November 18, 1908.

' mm a. cameo.

To all whom it may concern:

Be it known that I, PAUL LOUIS Toussnm'r HnRouLT, a citizen of the Republic of France, residing in La Praz, Savoie, France, have invented certain new and useful Improvements in Methods ofO crating Electric Furnaces, of which the 0 lowing is a specification.

This ap mention is a division of my application for patent for an improvement 1n electric furnaces and methods. filed May 3, 1907, No. 371,691.

The invention aims to provide for the varying of the arc gap in arc furnaces, or of the degree of contact in incandescent furnaces, so as to control in either case the current passin through the furnace with the use 0 an e ectrode which is fixed, at least during operation. This fixity of the electrode serves to eliminate various difliculties encountered in previous types of furnace in which the electrode has had to be adjusted through a water-cooled st'uifing-box, and in which the construction of this stuffing-box and also of the connections and supports of the outer end of the electrode were more or less complicated.

According to my present invention the face of the charge which is opposite the end of the electrode is moved toward and from the electrode, bein at the same time retained in a position arzillel to itself. This movement of the c arge is adapted to vary the resistance and consequently the current by shortening the gap in an arc furnace or by varying t e degree of contact with the electrode in an incandescent furnace. 'The face of the char e is preferably maintained parallel to itseFf by bein fed on an inclination corresponding with t e natural slopeofthe material, this slope being approximately the same for all dry substances which might be used in electric furnaces. Such a slope or inclination maintains itself always at about the same angle, depressions which occur therein during the operation of the furnace being automaticall filled up.

Various other eatures of improvement are referred to in detail hereinafter. The accompanying drawings illustrate embodiments of the invention.

Figure 1 is a longitudinal section approximate y on the line 11 of Fig. 2. Fig. 2 is a horizontal section approuimately on the .ra le.

terial. The material is fed in to the furnace by way of a shaft D of less diameter than the body of the furnace in proportion to the length of the overhanging walls G.

charge E, which may, for example, be of iron ore and coke, is in the form of a verti-fcal or approximately vertical column which spreads out below'the overhanging walls 0, and maintains a slope F which is approximately 42 degrees. The overhanging of the walls 0 is made just sufficient to provide a trian ular space G which will accommodate the e ectrode and slide hereinafter referred to. The corner of the overhanging walls C is preferably provided with a circulating pi e H for cooling it, so' as to make it du- Into the triangular space G is extended the end of one or more electrodes J, and the end of the electrode is tapered ofi so as to be parallel to the slope F, or will taper itself 1n a short time. The electrode may pass through a bushing K, cooled or not as desired, and which may serve as a con tact or cap L, with the usual connections to the cable M, may be provided, and provision may also be made for adjusting the electrode, as by means of the screw N indicated in Fig. 1.

The movement of the charge is effected by means of a slide 0 which is adapted to be withdrawn under the edge of the overhanging wall C, as shown in full lines, or to be projected sufliciently to move the slope F back to the dotted line F. This slide, for example, may be a flat plate (water cooled, if necessary) of a sufiicient breadth to cover the electrode and protect it from the charge at the sides, and may be rovided with a screw P at the'outer end ormanipulating it. A bushing Q may be provided where it passes through the wall of the furnace. This arrangement is adapted for furnaces utili ing either a on inuous or an alternating current, and for either a single pair of terminals or any multiple arrangement. For example, in Fig. 2 it is indicated as applied to a three-phase system, the generators R having one terminal connected to the electrodes respectively, and the other terminal connected to the carbon base A of the furnace. The current will pass from any one generator to the corresponding electrode, thence through the arc and through the more or less reslstant solid charge E to the liquefied portion S of the charge which collects at the bottom of the furnace, and thence out by way of the carbon base. The term arc furnace as used here is applied to furnaces of the type shown in Figs. 1, 2 and 3 in which there is an are employed, notwithstanding the fact that the current after jumping the arc passes through the charge in the same manner as in an incandescent furnace; the term incandescent being applied only to the type of furnace which operates entirely on the incandescent principle without the use of any definite arcs.

Instead of arranging the system with a star connection as shown, the bottom connection of the furnace may be suppressed and the electrodes arranged in a triangular connection, in which case it will operate as in other well known three-phase furnaces, the current passing from one electrode to the others. By adjustin the electrode J inwardly until it makes contactv with the charge, the furnace will operate as an incandescent furna'ce exclusively. The depth and other dimensions of the furnace may be so designed as to adapt it for use either as an incandescent or as an arc furnace. For arc furnaces the end of the electrode should be faced off approximately parallel to the charge. But it is immaterial in what direction the electrode itself lies. it ma bearranged vertically, as shown in full hnes at J 1n Fig. 3, or obliquely, as shown in dotted lines at J Likewise the means for shifting the charge toward and from the electrode may: be difierently arranged. For example, a vertical slide 0 may be used, as in Fig. 3, lying against the inner face of the shaft D and adjustable Vertically and held in position as by a screw T. For an incandescent furnace the electrode J F ig. 4, may be arranged in such a position as to be always in contact with the charge E over a greater or less portion of the face of the electrode, thus increasing or diminishing the resistance without varying the character of the furnace. The same means may be used in shifting the charge as are proposed in connection with furnaces of the arc type.

Furnaces of this type have the great ad vantage that they may be open at the top. The escaping gases may be freely burned, and the com ustion may be utilized to pre- For example,

heat the charge. For example, the shaftD may be extended upwardly sufiiciently to form a'chimney through which pass one or more tubes U carrying the charge and emptying into the body E of the charge. Supposing the smelting of iron ore to be under consideration, the lower ends of the tubes U, may be placed at approximately the point where the rising carbon monoxid has accomplished the reduction of the ore to the fullest extent possible, and has been so far converted into carbon dioxid that the mixture may be said to be saturated with the latter, so that if the gases passed any further through the charge there would be a burning of the coke which would counterbalance or overbalance the reduction of the ore. At this point the escaping gases may be burned, belng rich in carbon monoxid, and the heat of combustion will be transmitted through the tubes U or by any other means to the charge therein, thus lessening the work of the current by an amount which would otherwise be necessary for supplying a large number of heat units.

In the ordinary furnace with a vertical electrode about which the charge passes, there is at the lower corners of the electrode a forced contact with the charge, of which particles of molten iron absorb portions of the electrode so as to eat away its end. By the passing of the current to the inclined faceof the charge as shown, any contact of the charge with the electrode may be avoided, and this eating away of the end of the electrode may be eliminated. Again, with the ordinary vertical electrode there is formed immediately about the arc carbon monoxid, and a slight di tance above the arc carbon dioxid, which attacks the sides of the electrode, (especially on account of its temperature being higher than that of the adj acent charge), and burns it, so that the end of the electrode is reduced to the shape of a knob connected by a smaller neck with the upper part of the electrode. But by feeding the charge on an incline as shown, the end of the electrode is in a substantially permanently closed space and is not exposed to any of the gases except the carbon monoxid formed immediately about it and which is not oxidizing. These advantages are irrespective of the fixity or movability of the electrode' The furnace is not claimed in the present application, being claimed in myprevious application above referred to.

Though I have described with great particularity of detail certain embodiments of my invention, 'yet it is not to be understood therefrom that the invention is restricted to the particular embodiments disclosed.

Various modifications may be made by those skilledin the art without departure from the invention.

furnace which consists in feeding the charge so as to present an inclined face to an elec- 15 trode, andishifting said inclined face toward and from the electrode to vary the resistance.

In Witness whereof, I have hereunto signed my name in the presence of two subscribing 20 witnesses.

PAUL LOUIS TOUSSAINT HEROULT.

Witnesses:

DOMINGO A. USINA, THEODORE T. SNELL. 

